1. Field of the Invention
The present invention relates to a special type bearing device making use of a new type of high-tech eco-material (state-of-the-art material having excellent ecological adaptability) which is different from conventional industrial material in that biomass resources are utilized.
2. Description of the Related Art
For conventional special type bearing devices, copper-based or iron-based sintered alloys, polymer resin materials (nylon, Teflon, other synthetic resin, and so forth), and non-ferrous materials, such as phosphor bronze, brass and so forth, have been in widespread use, however, each of these materials have its own problem.
Conditions required of special type bearing devices include a small friction coefficient, low susceptibility to the effect of temperature, ease in fabrication, low cost, and slight offensiveness towards mating members.
None of the various conventional materials described above can satisfy all these conditions as required.
For example, the copper-based sintered alloy is soft and has a large friction coefficient, so that it is susceptible to the effect of change in temperature while its wear resistance is less than satisfactory depending on its application.
The iron-based sintered alloy has problems in that it is inferior in affinity and conformability with mating members, incapable of raising its oil retention ratio to a sufficiently high level, has a high expansion coefficient and so forth.
As for the polymer resin material, it is in principle intended for use in the case of dry friction where no lubricating oil is used, and its application is limited to the cases of use under a light load, use in a dry condition, and so forth. Further, it has problems such as limitations to enhancement of friction coefficient as well as wear resistance besides a problem of thermal expansion.
Meanwhile, the non-ferrous material described above can exhibit a function of satisfactory lubrication in its application under a high load, at low revolutions and so forth, however, it is not necessarily satisfactory in respect of friction coefficient, and wear resistance.
Now, an attempt to obtain a porous carbonaceous material by utilizing rice bran, produced in quantity of 900,000 tons a year in Japan and in as much as 33 million tons a year throughout the world, has been well known by researches carried out by Mr. Kazuo HOKKIRIGAWA, the first inventor of the present invention (refer to “Functional Material”, May issue, 1997, Vol. 17, No. 5, pp. 24˜28).
Herein are disclosed a carbonaceous material (referred to hereinafter as RB ceramic) obtained by mixing degreased bran derived from rice bran with a thermosetting resin, kneading, drying a formed kneaded mixture obtained by pressure-forming a kneaded mixture, and subsequently, firing the formed kneaded mixture as dried in an inert gas, and a method of producing the carbonaceous material.
With such a method as described above, however, it has been practically difficult to form the formed kneaded mixture with high precision because there occurs discrepancy in dimensions by as much as 25% in terms of a contraction ratio of the dimensions of a finished formed product obtained after firing in the inert gas to those of the formed kneaded mixture prepared by pressure-forming.
It is therefore an object of the invention to solve drawbacks of the conventional special type bearing units described above, and to provide a special type bearing device capable of satisfying all the requirements as described, that is, a special type bearing device that is insusceptible to damage, is light in weight, has a long service life and excellent wear resistance, is insusceptible to the effect of variation in temperature, is easy to fabricate, and has little offensiveness towards mating members, the special type bearing device further being capable of sufficiently retaining a lubricant such as oil and grease, and retaining the lubricant for a long period of time without the need of supplying oil during operation, thereby being rendered maintenance-free.